This invention relates to light-emitting or receiving devices (or parts) such as LED, laser diodes, and photosensors, and more particularly, to encapsulants having improved weatherability, chemical resistance, hardness, and optical properties and light-emitting or receiving devices using the same and having such improved properties.
This invention further relates to an encapsulating method useful in the manufacture of light-emitting or receiving devices.
In the prior art manufacture of light-emitting or receiving devices such as LED, laser diodes, and photosensors, light-emitting diodes and similar elements are encapsulated by casting epoxy resin followed by polymerization.
The encapsulating method using epoxy resin, however, has the following drawbacks.
(1) Since the epoxy resin has poor weatherability, its outdoor use is substantially limited. This is because light-emitting elements experience a drastic drop in luminous power with a lapse of time and light-receiving elements experience a drop in light-receiving sensitivity with a lapse of time when used outdoors.
(2) Since it takes a long time of 5 to 20 hours to cure the epoxy resin, the productivity of light-emitting or receiving devices is low.
(3) Since the epoxy resin has poor mold release characteristics, the productivity of light-emitting or receiving devices is low.
If a mold release agent is used to improve mold release, it is necessary to remove the mold release agent adhered to the surface of the epoxy resin encapsulant, creating a serious problem in the production process.